Muteins of various lipocalins are a rapidly expanding class of therapeutics. Indeed, lipocalin muteins can be constructed to exhibit a high affinity and specificity against a target that is different than a natural ligand of wild type lipocalins (e.g., WO 99/16873, WO 00/75308, WO 03/029463, WO 03/029471 and WO 05/19256), such as Interleukin-17A or Interleukin-23.
A. Interleukin-17A
Interleukin-17A (IL-17A, synonymous with IL-17) is a cytokine produced from the Th17 lineage of T cells. IL-17 was originally designated “CTL-associated antigen 8” (CTLA-8) (Rouvier et al., J. Immunol, 150 5445-5556 (1993); Yao et al., Immunity, 3: 811-821 (1995)). The human equivalent of CTLA-8 was later cloned and designated “IL-17” (Yao et al., J. Immunol, 155(12): 5483-5486 (1995); Fossiez et al., J. Exp. Med., 183(6): 2593-2603 (1996)).
Human IL-17A (CTLA-8, further named as IL-17, Swiss Prot Q16552) is a glycoprotein with a Mr of 17,000 daltons (Spriggs et al., J. Clin. Immunol, 17: 366-369 (1997)). IL-17A may exist as either a homodimer IL-17 A/A or as a heterodimer complexed with the homolog IL-17F to form heterodimeric IL-17 A/F. IL-17F (IL-24, ML-1) shares a 55% amino acid identity with IL-17A. IL-17A and IL-17F also share the same receptor (IL-17RA), which is expressed on a wide variety of cells including vascular endothelial cells, peripheral T cells, B cells, fibroblast, lung cells, myelomonocytic cells, and marrow stromal cells (Kolls et al., Immunity, 21: 467-476 (2004); Kawaguchi et al., J. Allergy Clin. Immunol, 114(6): 1267-1273 (2004); Moseley et al., Cytokine Growth Factor Rev., 14(2): 155-174 (2003)). Additional IL-17 homologs have been identified (IL-17B, IL-17C, IL-17D, IL-17E). These other family members share less than 30% amino acid identity with IL-17A (Kolls et al., 2004).
IL-17A is mainly expressed by Th17 cells and is present at elevated levels in synovial fluid of patients with rheumatoid arthritis (RA) and has been shown to be involved in early RA development. IL-17A is also over-expressed in the cerebrospinal fluid of multiple sclerosis (MS) patients. In addition, IL-17 is an inducer of TNF-α and IL-1, the latter being mainly responsible for bone erosion and the very painful consequences for affected patients (Lubberts E. (2008) Cytokine, 41, p. 84-91). Furthermore, inappropriate or excessive production of IL-17A is associated with the pathology of various other diseases and disorders, such as osteoarthritis, loosening of bone implants, acute transplant rejection (Antonysamy et al., (1999) J. Immunol, 162, p. 577-584; van Kooten et al. (1998) J. Am. Soc. Nephrol., 9, p. 1526-1534), septicemia, septic or endotoxic shock, allergies, asthma (Molet et al., (2001) J. Allergy Clin. Immunol., 108, p. 430-438), bone loss, psoriasis (Teunissen et al. (1998) J. Invest. Dermatol, 111, p. 645-649), ischemia, systemic sclerosis (Kurasawa et al., (2000) Arthritis Rheum., 43, p. 2455-2463), stroke, and other inflammatory disorders.
Although a variety of inhibitors of IL-17A have been described, since the discovery of this critical proinflammatory cytokine, current approaches are not optimal, such as the necessity of complex mammalian cell production systems, a dependency on disulfide bond stability, the tendency of some antibody fragments to aggregate, limited solubility and last but not least, they may elicit undesired immune responses even when humanized. There remains a need, therefore, to develop proteins such as lipocalin muteins with binding-affinity for IL-17A.
B. Interleukin-23
Interleukin-23 (also known as IL-23) is a heterodimeric cytokine comprised of two subunits, i.e., p19 and p40 (B. Oppmann et al, Immunity 13, 715 (2000)). The p19 (Swiss Prot Q9NPF7, herein referred to interchangeably as “IL-23p19”) subunit is structurally related to IL-6, granulocyte-colony stimulating factor (G-CSF), and the p35 subunit of IL-12. IL-23 mediates signaling by binding to a heterodimeric receptor, comprised of IL-23R and IL-12beta1. The IL-12beta1 subunit is shared by the IL-12 receptor, which is composed of IL-12beta1 and IL-12beta2. Transgenic p19 mice have been recently described to display profound systemic inflammation and neutrophilia (M. T. Wiekowski et al, J Immunol 166, 7563 (2001)).
Human IL-23 has been reported to promote the proliferation of T cells, in particular memory T cells and can contribute to the differentiation and/or maintenance of Thl 7 cells (D. M. Frucht, Sci STKE 2002 Jan. 8; 2002(114):PE1).
Although a variety of selective inhibitors of IL-23 (via binding to the p19 subunit) have been described, since the discovery of this critical heterodimeric cytokine, these current approaches still have a number of serious drawbacks, such as the necessity of complex mammalian cell production systems, a dependency on disulfide bond stability, the tendency of some antibody fragments to aggregate, limited solubility and last but not least, they may elicit undesired immune responses even when humanized. There is an unmet need to, therefore, to develop proteins such as lipocalin muteins with binding-affinity for IL-23.